1. Field of the Invention
The invention is related to the field of communications and, in particular, to defining dynamic service triggers in communication networks. More particularly, application servers (AS) in a communication network define service triggers to indicate which messages they want or need to receive for a session.
2. Statement of the Problem
One type of communication network gaining popularity is an IP Multimedia Subsystem (IMS) network. As set forth in the 3rd Generation Partnership Project (3GPP) or 3GPP2, IMS provides a common core network having access-agnostic network architecture for converged networks. Service providers are accepting this architecture in next generation network evolution. The IMS architecture is initially defined by the 3GPP to provide multimedia services to mobile subscribers over an Internet Protocol (IP) network, as IP networks have become the most cost savings bearer network to transmit video, voice, and data. The signaling used within IMS networks is typically Session Initiation Protocol (SIP). IMS defines the standard SIP interface between application servers, the IMS core network (CSCF), and the IMS subscriber. These standards can reduce the network integration costs and let the subscriber enjoy more stable services.
In an IMS network, user equipment of a calling party registers with the IMS network through an access network, such as a CDMA network, a GSM network, an IP network, a WiFi network, a WiMAX network, etc. Registration is typically performed by the user equipment transmitting a SIP REGISTER message to the access network. The access network routes the REGISTER message to the IMS network. A serving-call session control function (S-CSCF) in the IMS network receives the REGISTER message. The S-CSCF that is serving the user equipment of the calling party is referred to as the originating S-CSCF. Responsive to receiving the REGISTER message, the originating S-CSCF queries a Home Subscriber Server (HSS) for a user profile for the calling party. The user profile includes Initial Filter Criteria (iFC) that indicates service triggers and other triggering information for one or more services subscribed to by the calling party. The originating S-CSCF then stores the iFC for the calling party.
To initiate a session with a called party, the user equipment of the calling party transmits a SIP INVITE message to the IMS network through the access network. The INVITE message may be considered the session initiation message. The originating S-CSCF receives the INVITE message, and processes the iFC to determine which services may be triggered responsive to the INVITE message. If one or more services are triggered, then the originating S-CSCF identifies the application servers (AS) that provide such services in the IMS network, and also identifies routing information for the application servers. The originating S-CSCF then routes the INVITE message to the application servers based on the routing information.
The application servers receive the INVITE message and operate in a manner to provide a service or initialize a service. The originating S-CSCF then transmits the INVITE message to another S-CSCF that is serving user equipment of the called party. The S-CSCF that is serving the user equipment of the called party is referred to as the terminating S-CSCF. The terminating S-CSCF and the originating S-CSCF then attempt to establish the session.
As part of establishing or maintaining the session, the originating S-CSCF receives subsequent messages from the terminating S-CSCF and the user equipment of the calling party. Subsequent messages comprise any messages that are received subsequent to the session initiation message. For instance, originating S-CSCF may receive a SIP 183 message or a SIP 200 OK message from the terminating S-CSCF, or may receive a SIP UPDATE message from the user equipment of the calling party. Responsive to receiving a subsequent message for the session, the originating S-CSCF identifies the application servers that are in the signaling path established during session initiation. The originating S-CSCF then transmits the subsequent message to each of the application servers. The same process is repeated for each subsequent message that the originating S-CSCF receives for the session. A similar process is performed in the terminating S-CSCF.
One problem with present IMS networks is that the S-CSCF transmits subsequent messages to all of the application servers that are providing a service for the session as triggered by the iFC, even if the application servers do not need to receive the subsequent message to perform the service. As an example, assume that an application server provides a prepaid service for a session. The application server needs to be notified when the session starts and ends to determine prepaid charging information for the session, but may not need to be notified of other status-type messages, such as a SIP 183 message or a SIP UPDATE message. In this example, the application server will receive one or more subsequent messages from the S-CSCF even though the application server does not need to receive these subsequent messages. Transmitting unnecessary messages between an S-CSCF and application servers may congest the network, may produce longer call setup delays, and may waste processing time in the network nodes that have to process these unnecessary messages.